Process for the production of color images by the silver dyestuff bleaching method



United States Patent 3,340,060 PROCESS FOR THE PRODUCTION OF COLORIMAGES BY THE SILVER DYESTUFF BLEACH- ING METHOD Armin Meyer and Ren vonWartburg, Basel, and Walter Anderan, Aesch, Basel-Land, Switzerland,assignors to Ciba Limited, Basel, Switzerland, a Swiss company NoDrawing. Filed Sept. 24, 1963, Ser. No. 311,235

7 9 Claims. (CI. 96-53) The present invention provides a process for theproduction of color photographic images by the silver dyestufi bleachingmethod. As is known, this method depends on the fact that dyestufis,especially azo dyestuifs, are destroyed by a suitable treatment in thepresence of metallic silver and treatment in a neutral or an acid bathcontaining a complex-forming agent and a bleaching catlyst. The generalconception is that theoretically the bleaching of the dyestuffs proceedsstoichiometrically in accordance with the amount of silver present, foursilver atoms being required to destroy one azo group. It could thereforebe assumed that, in material containing a plurality of silver componentimages, the gradations of the color component images would depend solelyupon the gradations of the developed silver images. However, this is notthe case. The gradations of the color component images are dependent onmany other factors, for example, on the kind of dyestuffs used, on thecolloid layer, on the thickness of the layer, on the manner in which thesilver is distributed within the layer, on the composition of thebleaching bath and on the duration of the bleaching process.

Proposals 'for independently controlling the gradations of the colorcomponent images, especially for obtaining flatter gradations, havealready been made, for example, by the incorporation of non-diliusingbleaching catalysts in the light-sensitized layers, by the use ofoxidizing agents in the bleaching process and by the use of severalbleaching baths.

This invention is based on the surprising observation that speciallyadvantageous effects can be obtained in the production of colorphotographic images by the silver dyesruii bleaching method with the aidof catalyst when the development is carried out in a bath that containsa dyestutf bleaching catalyst under conditions such that the catalystplays no essential part in the development process.

The photographic material to be used may be, for example, materialcomprising a layer support, a cyan-color layer, a magneta-color layerand a yellow-color layer disposed one on top of the other in that order,each layer being made of a hydrophilic colloid such as gelatine andcontaining a latent silver image. The layers can also be present in thematerial in other sequences; the material can contain colored particlesof the mixed-grain emulsion type instead of the layers; the support canbe transparent or reflecting, and the material may also contain furtherlayers, for example, adhesive layers, intermediate layers, filter layersand covering layers. This material may also contain the usual emulsionadditives such as wetting agents, optical and chemical sensitizers; evensmall amounts of bleaching catalyst may be present in one or more layersor intermediate layers.

In the process of the invention the bath in which the latent silverimage is developed contains a dyestnff bleaching catalyst. Accordingly,a proportion of the dyestufi bleaching catalyst is taken up by thelayers of the photographic material being treated in the developing bathand it remains therein, at least partly, until it becomes active duringthe bleaching process.

The dyestufi bleaching catalysts must take no essen- 3,340,060 PatentedSept. 5, 1967 ice tial part in the development of the latent silverimage. This can easily be arranged by using developers virtuallyincapable of catalyzing the dyestuii bleaching process, which is thecase with most of the developers normally used. However, it is alsopossible to use a dyestuti bleaching catalyst that is not capable ofdeveloping a latent silver image in order to meet the requirement thatthe catalysts should take no essential part in the development process.It is also possible to combine the two conditions just mentioned; thatis to say, the developer used is incapable of catalyzing the bleachingprocess and the catalyst used is incapable of developing a latent silverimage.

It can easily be deter-mined by tests whether or not developers anddyestutf bleaching catalysts meet these requirements. As an example of adeveloper having no catalytic action on dyestuif bleaching there may bementioned hydroquinone, which is widely used, and which, it necessary,may be used together with other developers, for example, Metol.

As examples of dyestufi bleaching catalysts there may be mentionedphenazines, for example, 2-hydroxy-3- aminophenazine and2:3-diaminophenazine, but more especially phenazine compounds of theformula in which R represents a naphthalene radical condensed with theazine ring in the manner indicated by the valence lines, whichnaphthalene radical contains a hydroxyl, amino and/ or an azo groupattached to the six-membered ring not directly bound to the azine ring,and R represents a benzene or naphthalene radical bound to the azinering in the manner indicated by the valence lines. Such compounds andprocesses for their preparation are described in U.S. patent applicationSer. No. 306,690, filed Sept. 5, 1963, now U.S. Patent 3,318,700 (Swisspatent application No. 10,928/ 62).

Quinoxaline, alloxazine and cinnoline can also be used as dyestufibleaching catalysts.

The process of the present invention is carried out by known methods.

The dyestufi bleaching bath comprises, as usual, an acid aqueoussolution, for example, hydrochloric acid and at least onecomplex-forming agent, for example, potassium bromide or thiourea. Thisbath, too, can contain small amounts of bleaching catalyst. However, theamounts of catalyst that may be present in the material and/or in thebleaching bath must be such that they are not sufiicient to bring aboutcomplete bleaching of all the color component images by the image silverpresent in the time available.

Accordingly, a preferred method of carrying out the process of thepresent invention consists in exposing in the usual mannerlight-sensitive multilayer material that is colored with azo dyestufisand free from bleaching catalysts, developing it in a bath that containsa bleaching catalyst, fixing it, washing it with water, bleaching it ina bath free from catalyst, and then freeing it from residual silver inthe usual manner. The fixing bath between the developing bath anddyestuflz' bleaching bath may be omitted.

The method can also be applied in reversal processes, the catalyst beingadded to the second developing bath.

In the process of the present invention the catalyst exerts a veryuniform action in the various layers and exhibits favorable behaviour inrespect of diffusion, so that no over-bleaching of the top layer occursas in the usual processes.

Finally, in contrast to the processes known hitherto it is possible, inthe process of the invention, to harmonize the color gradations in sucha manner that, when exposed-to white light, fiatcolor gradationcurves'a-re obtained that run parallel to one another, and that, whenexposed to one spectral color, steep gradation curves are obtained:Thus, when a color chart that includes a neutral.

grey wedge is copied an imageis obtained in which the grey wedge iscorrectly reproduced and in which the colors exhibit a high degree ofsaturation. Should this process lead to too stronga bleaching of thelower layers, a balanced bleach can be obtained ,by dividing thecatalyst between the developer and the dyestufl bleaching bath.

The following examples illustrate the invention. Unless otherwisestated, the parts and percentages are by weight.

EXAMPLE 1 7 The following layers are applied successively to a celluloseacetate film providedwith an'adhesive layer:

(1) Red-sensitive silver bromide emulsion in gelatine that contains thecyan dyestutf ofthe formula v (2) Ooo-HN on (IL-CH3. HO

N=NON=N Ho,s- S03H I (2) Gelatine intermediate layer. (3)Green-sensitive silver bromide emulsion in gelatine that contains themagenta dyestufi of the formula 17m, noi s (4)'- Yellow filter layerthat contains the dyestufi'of the formula (5) Blue-sensitivesilverbromide emulsion in gelatine; that contains the; yellow dyestutf of theformula and as precipitating agent amixture comprising a reactionproductof dicyanodiamidine and formaldehyde, a

small amount of sodium formate and sodium bisulphite.

(6) Gelatine protective layer.

h sfil iis xp ed o m s inds ey d e. as,

ol ow 1st exposure: in red light only 2nd exposurezin green light only3rd exposure: in blue light only I 4th exposure: in red, green and bluelightpthe exposures being so arranged that the 4th wedge appears aneutral rey ite",p cessin o I I I 0 C H: H: C

Hots

4 The images obtained are designated hereinafter as red wedge, greenwedge, blue wedge and grey wedge. The film is hardened in a formaldehydebath, washed with water and then developed for 6 minutes in the follow-5 ing developer, the temperature of the developer and all subsequentbaths being .24? C.

veloper:

1st experiment 10 milligrams of 2-amino-3-hydroxyphenanzinehydrochloride. 7

2nd experiment 4 milligrams of 3 (4? sulfophenylazo) --4hydroxybenzohdphenazine-Z-sulfonic acid (of. the Formula 6.

S 0 11 HgN SOH 3rd experiment 6 milligrams of3-amino-4-hydroxybenzo[a]phenazine- 2-sulphonic acid of the Formula '7.V

The film is; then treated in the following stop fixation bath without anintermediate wash with water:

Sodium acetate grams 10 Thiourea I do Glacial acetic acid cc 20 5oBulked with water to 1000 cc.

The film is washed with water. for 3 minutes and then bleached in adyestuff bleaching bath having the following composition:

Potassium bromide Q grams 100 Thiourea do 10 Hydrochloric acid (conc.)cc 1,25% aqueous solution of the addition product of 70 4 35 mols ofethylene oxide with 1 mol of octadecyl alcohol 'c 10 Bulkedwith water to1000 cc;

The time of treatmentin-this bath is so selected that it is justsuflicient to bring about complete bleaching of the dyestuffs -t ll. ersth hp ces osthi hly pose the said time of treatment having beendetermined by tests. It is as follows:

The film is then washed with water, the residual silver rehalogenated ina copper nitrate bath made strongly acid with hydrochloric acid, washedagain, fixed, washed and then dried.

When repeating these experiments but omitting the bleaching catalyst indeveloper I, only a very slight degree of dyestuti bleaching isobtained.

In three further experiments the same procedure as above is adopted butomitting the developers l-phenyl-3- pyrazolidone and hydroquinone indeveloper I. In this process no silver image is visible before thebleaching bath; on completion of the process no bleaching of thedyestuffs is observed.

The dyestuff in the blue-sensitive layer can be prepared by diazotizing2-aminonaphthalene-4:8-disulfonic acid, coupling the diazo compound with1-amino-2-methylbenzene, and treating the aminomonoazo dyestutt soobtained with phosgene.

The catalyst 3-(4'-sulfophenylazo) 4 hydroxybenzo-[a]phenazine-2-sulfonic acid of the formula HOsS N/ I \N Holsis obtainedfrom the foregoing catalyst by splitting the azo group with sodiumhydrosulfite.

EXAMPLE 2 The experiments described in Example 1 are repeated using thefollowing developer 11:

Grams Metol 2.5 Sodium sulfite (anhydrous) 30 Hydroquinone 2.5 Sodiummetaborate Potassium bromide 0.5

Bulked with water to 1000 cc.

The following bleaching catalysts are added to this developer, theamounts being in milligrams per liter of developer:

1 st experiment 4 milligrams of 2-amino-3-hydroxyphenazinehydrochloride.

2nd experiment 4 milligrams of 2-amino-3-hydroxyphenazine hydrochloride.

4 milligrams of 3-(4'-sulfophenylazo)-4-hydroxybenzo-[a1phenazine-2-sulfonic acid of the Formula 6.

3rd experiment at the areas most highly exposed is as follows:

Minutes 1st experiment 10 2nd experiment a '10 3rd experiment 12 Only avery slight degree of bleaching is achieved when the bleaching catalystis omitted in developer II. No silver image is visible and no dyestuffbleaching takes place when the two developers Metol and hydroquinone areomitted in developer II.

EXAMPLE 3 A film of the composition given in Example 1 is exposed,hardened in a formaldehyde bath, washed with water and then developedfor 4 minutes in developer I, which developer contains 30 milligrams of2-amino-3- hydroxy-phenazine hydrochloride per liter as bleachingcatalyst. The film is Washed with water for 2 minutes and then treatedfor 4 minutes in the dyestuif bleaching bath as described in Example 1which is free from bleaching catalyst. In accordance with Example 1, theresidual silver is then rehalogenated and fixed. The time of treatmentin the dyestuff bleaching bath is so selected that it is just sufficientto bring about complete bleaching of the dyestuffs in all layers at theareas most highly exposed, which time is determined by experiment.

For comparison purposes, a series of 4 exposures produced in the samemanner as above is subjected to the same treatment, with the exceptionthat the developer I is free from bleaching catalyst and the samecatalyst was added to the dyestuff bleaching bath in an amount of 2milligrams per liter. The minimum time required to bring about completebleaching is 8 minutes.

The results obtained in the two experiments in respect of gradation(gamma value) and extent of exposure are listed in the following table,the extent of exposure being designated with Alog E.

Alog E=10g mma min.

whereby Emax, and E represent the strongest and Weakest exposuresrespectively that are capable of being copied. The color densities aremeasured with a Macleth-Ansco- Densitometer in transmitted light; thegamma values correspond to the straight parts of the gradation curves.

| Boas 7 EXAMPLE 4i Multi-layer silver dyestuff. bleaching materialfcaston baryta paper and hardened while casting, but otherwise having thesame composition as 'inExample 1 is exposed and developed. The silver isconverted into silver chloride in a bleaching bath andthe resultingchloride dissolved out selectively. The silver bromide that remains isexposed in diffused light and-developed for 10 minutes in a developerhaving the following composition:

Bulked with water to 1000 cc.

This solution also contains 25 milligrams'of the dyestuft' bleachingcatalyst 3-amino-4-hydroxybenzo[u]phenazine- 2-sulfonicacid'ofthe'Formula- 7.

The-layer-is"then'washed with-Water'for 1 minute and bleached-for 8'minutes in a batlr having the following composition;

Water "millimeters", 75.0 Potassium bromide grams .100 Hydrochloric acid(37% strength) m illimeters 70 Thiourea grams 10" Bulked with water toLOOO'millimeters.

This bath also contains 1 milligram of the dyestutf bleachirig catalyst3-(4'.-snlfophenylazo) 4 hydroxybenzohz] phenazine-2-sulfonic acid ofthe Formula 6.

'The layer is washed with water and the excess silver converted intosilver chloride in known manner with the aid of a copper-containingbleaching bath, and the. chloride dissolved out in a subsequent fixingbath. The resulting color image exhibits high color densities atthehighly exposed'areas after the above treatment, and the dyestulfs arebleached out at the areas of low exposure.

EXAMPLE 5 A silver bromide-silver iodide emulsion that contains theblack dyestufi of the formula O-OHr and a hardening agent is cast on toa photographic paper;

A sheet of type-Written paper is brought intocontact with the saidphotographic paper in such a manner thatthe back of the original lies'on thephotographic layer.

The composite specimen is exposed for 15 seconds in a Whenthe2c3-dimethylquinoxaline solution is omitted from the developer, nodyestuff bleaching takes place and a completely black sheet of paper isobtained.

What is claimed is: 1. In a process for the production of c010!Photographic fl f I I s'oai 1101's images by. the silver 'dyes tufibleaching method with the aid of catalysts, the step which comprisescarrying out the development in a bath that contains a dyestufl?bleaching catalyst and undervconditions such that the catalystplayssnoessential part inthe developmentprocess.

2. In a process forthe production ofcolor photographic images bythesilver dyestufi bleaching method with the aid of catalysts, the stepwhich comprises carrying out the development in a bath that contains adeveloper not,

capable of catalyzing the dyestuif bleaching process and also a dyestuifbleaching catalyst.

3. In a process for the production of color photographic aid ofcatalysts, the step which comprises carryingout the.

development in a bath that contains a developer not ca-, pable ofcatalyzing the dyestuflf bleaching process and also a'phenazine as adyestutf bleaching catalyst.

5. Ina process for the production of colorphotographic images bythesilver dyestutf bleaching-method withtheaid of catalysts, the stepwhich comprises carrying out the development in a bath that contains adeveloper not capable of catalyzing the dyestufi bleach-ing process andalso a quinoxaline as a dyestuif bleaching catalyst.

6. In a process-for the production of multi-color photographic images bythe silver dyestutf bleaching method with the aid of catalysts, the stepwhich comprises carrying out the developmentin a. bath that containshydroquinone as a developer and also a phenazine as a dyestutf bleachingcatalyst.

7. In a process for the production of multi-color photographic images bythe silver dyestuif bleaching method with the aid of catalysts, the stepwhich comprises carrying, out the development in a bath that containshydroquinone as a developer and also 2,-amino-3-hydroxyphenazine.as a,

dyestufi bleaching catalyst.

with the aid of catalysts, the step which comprises carry- HsC-O SOBHing out the development in a bath that contains hydroquinone as adeveloper andalso3-(4l-sulfophenyl'azo)-4-hydroxybenzo[aJphenazine-Z-sulfonic acid as adyestuft bleaching catalyst.

9. In a process for-the production of multi-color photo! graphic imagesby the silver dyestufi"bleachingmethod.

with the aid of catalysts, the step which comprises carrying out thedevelopment in a bath'that contains hydroquinone as a. developer 7 andalso 3.-amino-4-hydroxybenzo lyst.

References Cited UNITED-STATES PATENTS' .J. TRAVIS BROWN, PrimaryExaminer.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,340,060 7 September 5 1967 Armin Meyer et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the heading to the printed specification, after line 8 insert Claimspriority, application Switzerland, Oct. 5, 1962, 11760/62 Signed andsealed this 22nd day of October 1968 (SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer

1. IN A PROCESS FOR THE PRODUCTION OF COLOR PHOTOGRAPHIC IMAGES BY THESILVER DYESTUFF BLEACHING METHOD WITH THE AID OF CATALYSTS, THE STEPWHICH COMPRISES CARRYING OUT THE DEVELOPMENT IN A BATH THAT CONTAINS ADYESTUFF BLEACHING CATALYST AND UNDER CONDITIONS SUCH THAT THE CATALYSTPLAYS NO ESSENTIAL PART IN THE DEVELOPMENT PROCESS.